Additive for communication cable filler and filler for communication cable

ABSTRACT

The additive (b) for a communication cable filler according to the present invention contains as a main component an ethylene/α-olefin copolymer (a) having a number-average molecular weight (Mn), measured by GPC, of 500 to 5,000 and having a crystallizing temperature (Tc (° C.), rate of temperature decrease: 2° C./min) measured by DSC and a density (D (kg/m 3 )) measured by a density gradient tube method, said Tc and D satisfy the following formula (1): 
     0.501× D (kg/m 3 )−366≧ Tc (° C.)  (1). 
     The communication cable filler (c) according to the invention is prepared by blending (X) 40 to 90% by mass of polybutene (d) having a number-average molecular weight of 200 to 2,400, (Y) 1 to 50% by mass of an oil (e) and (Z) 1 to 15% by mass of the ethylene/(α-olefin copolymer (a). The additive for a communication cable filler and the communication cable filler are excellent in the filling workability and the oil retention properties of a cable jelly.

FIELD OF THE INVENTION

[0001] The present invention relates to an additive for a communicationcable filler and a communication cable filler. More particularly, theinvention relates to an additive for a communication cable filler, whichcomprises an ethylene/α-olefin copolymer having various excellentproperties and available at a low cost, and to a communication cablefiller having various excellent properties and available at a low cost,which is prepared by blending a given amount of the additive withpolybutene and an oil.

BACKGROUND OF THE INVENTION

[0002] If armors or joints of communication cables, particularly thoseof communication cables for underground buried wiring are damaged ordeteriorated, infiltration of water into the cables brings to impairmentof electric transmission characteristics of the cables. Moreover, if apinhole is present in the insulators of the cables, insulation isreduced by infiltration of water, and at last a short circuit takesplace to sometimes bring about an accident of wire breaking.

[0003] To prevent circuit troubles due to infiltration of water intocables, development of waterproof communication cables has been made anda great number of communication cables filled with jelly-like fillingmaterials came to be employed.

[0004] As the jelly-like filling materials, blends of petroleum jellysuch as petrolatum, polybutene, atactic polypropylene (PP), mineral oil,various waxes and the like are generally employed, and they are publiclyknown. Especially for thick cables, there is no filling materialssatisfying all the requirements such as waterproof properties,electrical properties, dropping properties, melting point, consistencyand workability, and filling materials obtained by adding blends topetrolatum are mainly employed. From the viewpoints of cost and supplystability, however, formulations mainly using polybutene areadvantageous. The “polybutene” referred to herein means polybutene in anarrow sense, namely, a liquid polymer of a pentamer to a pentacontamerobtained from a mixture of three isomers of n-1-butene, n-2-butene andisobutylene.

[0005] For the polybutene-based waterproof cable jellies, a great numberof formulations have been proposed, and it is also known to usepolyethylene (PE) wax, paraffin wax and microcrystalline wax asadditives. The reason why polybutene is used is that the volumeshrinkage after pouring of a jelly into the cable is minimized to impartflexibility to the cable, and an oil is added for the purpose ofreducing cost and adjusting fluidity. The PE wax is used to harden thejelly by cooling and thereby prevent oozing of oil, and 1 to 20% of thiswax is usually added.

[0006] In the filling work of a cable with a cable jelly having beenmelted at a high temperature, the temperature at which the molten cablejelly is cooled and hardened in the cable is desired to be as low aspossible. The reason is that it is required to fill the cable with thecable jelly in low viscosity more rapidly and in every nook and corner.On this account, the crystallizing temperature (Tc) of the PE wax todetermine the hardening temperature of the cable jelly is desired to beas low as possible.

[0007] On the other hand, the PE wax is also required to have oilretention properties to prevent oozing of the oil by hardening the oiland polybutene in the cable jelly. When Tc of the wax is decreased forthe purpose of decreasing the hardening temperature of the cable jelly,there arises a problem that the oil retention properties are alsoreduced at the same time. The reason is that decrease of crystallinityor crystallizability of the wax to decrease the Tc results in loweringof oil retention properties.

[0008] It is an object of the present invention to provide an additivefor a communication cable filler, which can satisfy both the fillingworkability and the oil retention properties of a cable jelly, and acommunication cable filler containing the additive.

DISCLOSURE OF THE INVENTION

[0009] The present inventors have synthesized various PE waxes in orderto solve the above problem and earnestly studied. As a result, they havefound that the above problem can be solved by an additive (b) for acommunication cable filler, which contains an ethylene/α-olefincopolymer (a) having a number-average molecular weight (Mn), measured bygel permeation chromatography (GPC), of 500 to 5,000 and having acrystallizing temperature (Tc (° C.), rate of temperature decrease: 2°C./min) measured by DSC and a density (D (kg/m³)) measured by a densitygradient tube method, said Tc and D satisfy a specific relation.

[0010] That is to say, the present invention is an additive (b) for acommunication cable filler, which contains as a main component anethylene/α-olefin copolymer (a) having a number-average molecular weight(Mn), measured by GPC, of 500 to 5,000 and having a crystallizingtemperature (Tc (° C.), rate of temperature decrease: 2° C./min)measured by DSC and a density (D (kg/m³)) measured by a density gradienttube method, said Tc and D satisfy the following formula (1):

0.501×D(kg/m³)−366≧Tc(° C.)  (1),

[0011] preferably the following formula (2):

0.501×D(kg/m³)−367≧Tc(° C.)  (2).

[0012] In the additive (b) for a communication cable filler according tothe invention, the ethylene/α-olefin copolymer (a) is desirably anethylene/α-olefin random copolymer obtained from ethylene and anα-olefin of 3 to 10 carbon atoms and having an ethylene componentcontent of 90 to 99 mol % and an α-olefin component content of 10 to 1mol %.

[0013] In the additive (b) for a communication cable filler according tothe invention, the ethylene/α-olefin copolymer (a) is preferably oneobtained by feeding ethylene, an α-olefin and hydrogen to thepolymerization system in the presence of a metallocene catalystcontaining as a main component a compound, having a cyclopentadienylgroup, of a transition metal selected from the group consisting oftitanium, zirconium, hafnium and vanadium to copolymerize ethylene withthe α-olefin.

[0014] In the additive (b) for a communication cable filler according tothe invention, a B value is calculated based on a chart of ¹³C-NMR (270MHz) of the ethylene/α-olefin copolymer (a) and expressed by thefollowing formula (3),

B=P _(OE)/(2×P _(O) ·P _(E))  (3)

[0015] wherein P_(E) is a molar fraction of the ethylene component inthe copolymer, P_(O) is amolar fraction of the α-olefin component, andP_(OE) is a molar fraction of α-olefin-ethylene sequences in the alldyad sequences, with the proviso that the molar fraction of eachcomponent is a value calculated except the terminal component,

[0016] and the B value satisfies the following formula (4),

1.0<B<2  (4).

[0017] The present invention to solve the aforesaid problem is also acommunication cable filler (c) containing as an essential component theabove-mentioned additive (b) for a communication cable filler andcomprising:

[0018] (X) 40 to 90% by mass of polybutene (d) having a number-averagemolecular weight of 200 to 2,400,

[0019] (Y) 1 to 50% by mass of an oil (e), and

[0020] (Z) 1 to 15% by mass of the ethylene/α-olefin copolymer (a).

[0021] The communication cable filler (c) according to the invention ispreferably one having properties that in the oil drip test (REA PE-39method, 80° C.×24 hr), any jelly and any oil do not fall from thefunnel, and after standing for 24 hours, the total amount of the jellyand the oil adhering inside the leg of the funnel is not more than 20mg.

PREFERRED EMBODIMENTS OF THE INVENTION

[0022] The present invention is described in detail hereinafter withreference to the following embodiments.

[0023] [Additive (b) for Communication Cable Filler]

[0024] The additive (b) for a communication cable filler according tothe invention contains as a main component an ethylene/α-olefincopolymer (a) having a number-average molecular weight (Mn), measured bygel permeation chromatography (GPC), of 500 to 5,000 and having acrystallizing temperature (Tc (° C.), rate of temperature decrease: 2°C./min) measured by a differential scanning calorimeter (DSC) and adensity (D (kg/m³)) measured by a density gradient tube method, said Tcand D satisfy the following formula (1):

0.501×D(kg/m³)−366≧Tc(° C.)  (1),

[0025] preferably the following formula (2):

0.501×D(kg/m³)−367≧Tc(° C.)  (2).

[0026] The density (D) of the ethylene/α-olefin copolymer (a) in theformulas (1) and (2) relates, in this case, to a proportion of crystals(i.e., crystallinity (%)) and quality of crystals (i.e.,crystallizability). If the type of the α-olefin is determined, thecrystallinity depends upon the content of the α-olefin, and thecrystallizability greatly depends upon the type of the α-olefin.

[0027] The density (D) in the formulas (1) and (2) is measured inaccordance with ASTM-D-1505-68, and in the pretreatment, the sample isplaced in a brass container, melted at 150° C. over a period of 1 hourin an electrical dryer and allowed to stand in a constant temperaturebath at 23° C. for not shorter than 3 hours.

[0028] Although the α-olefin to constitute the ethylene/α-olefincopolymer (a) for use in the invention is not specifically restricted,it is preferably an α-olefin of 3 to 10 carbon atoms, for example,propene of 3 carbon atoms, 1-butene of 4 carbon atoms, 1-pentene of 5carbon atoms, 1-hexene or 4-methyl-1-pentene of 6 carbon atoms, or1-octene of 8 carbon atoms. Particularly preferable is propene,1-butene, 1-hexene or 4-methyl-1-pentene.

[0029] The ethylene/α-olefin copolymer (a) for use in the invention isdesirably an ethylene/α-olefin random copolymer obtained from ethyleneand an α-olefin of 3 to 10 carbon atoms and having an ethylene componentcontent of 90 to 99 mol % and an α-olefin component content of 10 to 1mol %. The ethylene/α-olefin copolymer (a) has more desirably anethylene component content of 90 to 95 mol % and an α-olefin componentcontent of 10 to 5 mol %. When the α-olefin component content is in theabove range, the crystallinity (i.e., proportion of crystal component)of the ethylene/α-olefin copolymer (a) does not become too low, so thatwhen the copolymer (a) is used for a communication cable filler, thecommunication cable filler tends to be excellent in oil retentionproperties. When the α-olefin component content is in the above range,too much increase of the crystallizing temperature due to increase ofthe crystallinity does not take place, and workability in the productionof a communication cable filler tends to be excellent.

[0030] The crystallizing temperature (Tc (° C.)) in the formulas (1) and(2) was measured in accordance with ASTM D 3417-75, and the rate oftemperature decrease of DSC was decided to be 2° C./min in order toapproximate the rate of temperature decrease to the actual hardeningrate of the jelly.

[0031] There is no specific limitation on the process for preparing theethylene/α-olefin copolymer (a) as far as such an ethylene/α-olefincopolymer (a) as mentioned above can be prepared. However, it ispreferable to obtain the copolymer by feeding ethylene, an α-olefin andhydrogen to the polymerization system in the presence of a metallocenecatalyst containing as a main component a compound having acyclopentadienyl group, of a transition metal such as titanium,zirconium, hafnium and vanadium to copolymerize ethylene with theα-olefin.

[0032] As the metallocene catalyst, any of known catalysts employablefor the preparation of polyethylene is available, but particularlypreferable is a monocyclopentadienyl geometric constraint typemetallocene catalyst for high-temperature polymerization because thiscatalyst is excellent in copolymerizability of ethylene and the α-olefinand is easily adaptable to the process suitable for copolymerization inthe low-molecular weight region.

[0033] A co-catalyst employable in combination with the metallocenecatalyst is, for example, an alkylaluminum compound or a boron compound,and the co-catalyst can be used when needed.

[0034] The ethylene/α-olefin copolymer (a) for use in the invention hasa number-average molecular weight of 500 to 5,000, more preferably 500to 3,000, as described above. When the number-average molecular weightis in the above range, the melting point of the communication cablefiller does not become too low, and the consistency thereof does notbecome too large. When the number-average molecular weight is in theabove range, further, the melting viscosity of the communication cablefiller is moderate, and the workability tends to be excellent.

[0035] With respect to the ethylene/α-olefin copolymer (a) for use inthe invention, a B value is calculated based on a chart of ¹³C-NMR (270MHz) of the copolymer and expressed by the following formula (3),

B=P _(OE)/(2×P _(O) ·P _(E))  (3)

[0036] wherein P_(E) is a molar fraction of the ethylene component inthe copolymer, P_(O) is a molar fraction of the α-olefin component, andP_(OE) is a molar fraction of α-olefin-ethylene alternating sequences inthe all dyad sequences, with the proviso that the molar fraction of eachcomponent is a value calculated except the terminal component,

[0037] and satisfies the following formula (4),

1.0<B<2  (4).

[0038] With respect to the ethylene/α-olefin copolymer (a) for use inthe invention, a B value is desired to satisfy preferably the followingformula (4-a):

1.3-0.3×P _(E) ≦B<1/P _(E)  (4-a),

[0039] more preferably the following formula (4-b):

1.4-0.4×P _(E) ≦B<1/P _(E)  (4-b),

[0040] still more preferably the following formula (4-c):

1.5-0.5×P _(E) ≦B<1/P _(E)  (4-c).

[0041] The B value is an indicator of a distribution of the monomercomponents in the ethylene/α-olefin copolymer chains, and is calculatedby determining the above-defined values of P_(E), P_(O) and P_(OE) basedon the reports by G. J. Ray (Macromolecules, 10, 773 (1977)) , J. C.Randall (Macromolecules, 15, 353 (1982), J. Polymer Science, PolymerPhysics Ed., 11, 275 (1973)) and K. Kimura (Polymer, 25, 441 (1984)).

[0042] The composition distribution B value is determined as follows. A¹³C-NMR spectrum of a sample obtained by dissolving about 200 mg of thecopolymer in 1 ml of hexachlorobutadiene in a sample tube of 10 mm indiameter is usually measured under the measuring conditions of ameasuring temperature of 120° C., a measuring frequency of 25.0 MHz, aspectral width of 1500 Hz, a filter width of 1500 Hz, a pulse recurrencetime of 4.2 sec, a pulse width of 7 μsec and integration numbers of 2000to 5000, and from the spectrum, P_(E), P_(O) and P_(OE) are determined,followed by calculation.

[0043] A larger B value indicates that the copolymer has fewerblock-like chains, more homogeneous distribution of the ethylene unitsand the α-olefin units and narrower composition distribution. The Bvalue calculated by the above formula becomes 2 when the both monomersare alternately distributed in the ethylene/α-olefin copolymer, while itbecomes 0 in case of a complete-block copolymer wherein those monomersare completely separated from each other.

[0044] When an ethylene/α-olefin copolymer (a) having a B value in theabove range is used, a communication cable filler (c) being excellent inoil drip properties can be obtained.

[0045] With respect to the ethylene/α-olefin copolymer (a) for use inthe invention, further, any signals of αβ and βγ based on the methylenechain between adjacent two tertiary carbon atoms in the copolymer chainare not observed in the ¹³C-NMR spectrum.

[0046] For example, in a copolymer of ethylene and 4-methyl-1-pentene,central three methylene groups in the following bond are at thepositions of α, β and γ from the left-hand side when seen from theleft-hand tertiary carbon derived from 4-methyl-1-pentene, while theyare at the positions of α, β and γ from the right-hand side when seenfrom the right-hand tertiary carbon.

[0047] In the bond unit described above, therefore, methylene groups togive signals of αγ and ββ exist, but methylene groups to give signals ofαβ and βγ do not exist.

[0048] Likewise, in the following bond wherein 4-methyl-1-pentene groupsare head-to-tail bonded to each other, only a methylene group to give asignal of au exists, but methylene groups to give signals of αβ and βγdo not exist.

[0049] On the other hand, the following bonds have methylene groups togive a signal of βγ and methylene groups to give a signal of αβ,respectively.

[0050] and

[0051] As is apparent from the above description, the ethylene/α-olefincopolymer (a) for use in the invention exhibits regular bond directionsof the monomer copolymerized with ethylene.

[0052] The ethylene/α-olefin copolymer (a) can be used singly or incombination of plural kinds, as the additive (b) for a communicationcable filler according to the invention.

[0053] The additive (b) for a communication cable filler according tothe invention may further contain, as a gelatinizing agent,hydroxystearate, acrylic acid, methacrylic acid, a derivative or apolymer of acrylic acid and/or methacrylic acid, or a polyolefinelastomer (low-crystalline polymer or the like) containing ethylene,propylene or butene as a main component, in addition to theethylene/α-olefin copolymer (a).

[0054] The gelatinizing agent can be added in an amount of usually 0.1to 50 parts by mass, preferably 0.5 to 30 parts by mass, more preferably1 to 10 parts by mass, based on 100 parts by mass of theethylene/α-olefin copolymer (a).

[0055] In addition, publicly known additives, such as antioxidant, flameretardant and weathering stabilizer, can be added when needed.

[0056] The above-mentioned additives, such as gelatinizing agent,antioxidant, flame retardant and weathering stabilizer, can be added inan arbitrary way, and methods or techniques publicly known areapplicable.

[0057] [Communication Cable Filler (c)]

[0058] The communication cable filler (c) (sometimes referred to as“cable jelly” hereinafter) according to the invention comprisespolybutene (d), an oil (e) and the additive (b) for a communicationcable filler, which contains the ethylene/α-olefin copolymer (a) havingthe aforesaid specific properties.

[0059] In the communication cable filler (c) according to the invention,the ethylene/α-olefin copolymer (a) is added in such an amount that thecontent of the copolymer becomes usually 1 to 20% by mass, preferably 1to 15% by mass, more preferably 5 to 10% by mass, based on the totalamount of the cable jelly.

[0060] When the amount of the ethylene/α-olefin copolymer (a) added isin the above range, the hardening temperature of the cable jelly can besufficiently lowered, and after hardening, the cable jelly does notbecome brittle and tends to hardly suffer cracks such as crazes.

[0061] As the polybutene (d) that is a main component of thecommunication cable filler (c) of the invention, polybutene having anumber-average molecular weight of 200 to 2,400, preferably 500 to1,500, is used, and a commercially available one is employable.Hydrogenated polybutene obtained by hydrogenation of polybutene withnickel or the like by a known method is also employable.

[0062] When the number-average molecular weight of the polybutene (d) isin the above range, excessive softening of the cable jelly due to largeconsistency does not occur. Moreover, the cable jelly has a moderatemelt viscosity and tends to be excellent in workability. If thepolybutene (d) is not used, the cable jelly becomes too hard andexhibits insufficient electrical properties and waterproof properties,so that such a case is unfavorable.

[0063] In the communication cable filler (c) according to the invention,the polybutene (d) is used in an amount of usually 40 to 90% by mass,preferably 40 to 80% by mass, more preferably 50 to 70% by mass, basedon the total amount of the cable jelly.

[0064] When the amount of the used polybutene (d) is in the above range,the cable jelly does not become too soft and has a moderate viscosity inthe melting process. Moreover, the filling workability tends to beexcellent.

[0065] The oil (e) added for the communication cable filler (c) of theinvention may be a synthetic oil or a natural oil, and examples suchoils include mineral oil, fuel oil, industrial stock oil, waste oil andedible oil. More specific examples include liquid hydrocarbons, such askerosine, gas oil, crude oil, heavy oil, lubricating oil and liquidparaffin; fluid non-crystalline polymers, such as polybutene oligomer;and animal and vegetable oils used as edible oils, such as olive oil.

[0066] In the communication cable filler (c) according to the invention,the oil (e) is added in an amount of usually 1 to 50% by mass,preferably 10 to 50% by mass, more preferably 20 to 40% by mass, basedon the total amount of the cable jelly.

[0067] When the amount of the added oil (e) is in the above range, thecable jelly has a moderate viscosity and tends to be sufficientlyhardened to give a appropriate jelly.

[0068] The total amount of the ethylene/α-olefin copolymer (a), thepolybutene (d) and the oil (e) usually becomes 100% by mass. However, ifother arbitrary components are contained in the communication cablefiller (c), the total amount thereof becomes less than 100% by mass.

[0069] The oil (e) for use in the invention is desirably added in anamount of preferably 10 to 100 parts by mass, more preferably 40 to 60parts by mass, based on 100 parts by mass of the polybutene.

[0070] Although the communication cable filler (c) of the inventioncontains the polybutene (d), the oil (e) and the ethylene/α-olefincopolymer (a) as essential components, other components publicly knownin the field of cable jelly, such as atactic polypropylene, styreneelastomer and polyolefin elastomer, can be added when needed, so far asthe properties of the communication cable filler (c) of the inventionare not impaired. These arbitrary components are added in amounts ofabout 0.1 to 80% by mass, preferably about 10 to 20% by mass, based onthe total amount of the cable jelly.

[0071] The communication cable filler (c) of the invention preferablyhas properties that, in the later-described oil drip test (REA PE-39method, 80°C.×24 hr), any jelly and any oil do not fall from the funnel,and after standing for 24 hours, the total amount of the jelly and theoil adhering inside the leg of the funnel is not more than 20 mg,preferably not more than 5 mg.

[0072] Whether the jelly has fallen to a position lower than the conicalpart of the funnel is judged by visual observation, and the total amountof the jelly and the oil adhering inside the leg of the funnel ismeasured in the following manner. The jelly adhering inside the leg isscraped from the bottom of the funnel by a small spatula and is weighed.

[0073] The communication cable filler (c) satisfying the aboveconditions in the oil drip test has excellent ability to preventinfiltration of water into the communication cable when the outermostlayer of the cable is broken.

EFFECT OF THE INVENTION

[0074] According to the invention, an additive for a communication cablefiller, which can satisfy both properties of filling workability and oilretention properties of a cable jelly, and a communication cable fillercomposition can be provided, as described above.

EXAMPLES

[0075] The present invention is further described with reference to thefollowing examples.

[Preparation Example 1]

[0076] <Preparation of Ethylene/α-Olefin Copolymer>

[0077] An ethylene/α-olefin copolymer was prepared in the followingmanner using a metallocene catalyst.

[0078] In a 2-liter stainless steel autoclave thoroughly purged withnitrogen, 950 ml of hexane and 50 ml of propene were placed, andhydrogen was fed until the pressure in the system was reached 1.0 kg/cm²(gauge pressure). The temperature in the system was raised to 150° C.,and then 0.3 mmol of triisobutylaluminum, 0.004 mmol oftriphenylcarbeniumtetrakis(pentafluorophenyl)borate and 0.02 mmol of(t-butylamido)dimethyl(tetramethyl-η⁵-cyclopentadienyl)silane titaniumdichloride (available from Sigma-Aldrich Co.) were forced into theautoclave with ethylene to initiate polymerization. Thereafter, onlyethylene was continuously fed to maintain the total pressure at 30kg/cm² (gauge pressure), and polymerization was conducted at 150° C. for20 minutes.

[0079] After a small amount of ethanol was added to the system toterminate the polymerization, the unreacted ethylene and propene in thesystem was purged off. The obtained polymer solution was dried overnightat 100° C. under reduced pressure. As a result, 32.5 g of anethylene/propene copolymer (WAX 1) having Mn of 2,050, a propene contentof 7.3 mol %, a density of 920 kg/M³, a crystallizing temperature of 93°C. and a B value of 1.051 as shown in Table 1 was obtained.

[Preparation Example 2]

[0080] <Preparation of Ethylene/α-Olefin Copolymer>

[0081] Polymerization was carried out in the same manner as inPreparation Example 1, except that 935 ml of hexane and 65 ml of1-butene as an α-olefin component were placed and hydrogen was fed untilthe pressure in the system was reached 1.5 kg/cm² (gauge pressure). As aresult, 37.5 g of an ethylene/1-butene copolymer (WAX 2) having Mn of1,900, a 1-butene content of 5.6 mol %, a density of 920 kg/m³, acrystallizing temperature of 93° C. and a B value of 1.038 as shown inTable 1 was obtained.

[Preparation Example 3]

[0082] <Preparation of Ethylene/α-Olefin Copolymer>

[0083] Polymerization was carried out in the same manner as inPreparation Example 1, except that 920 ml of hexane and 80 ml of1-hexene as an α-olefin component were placed and hydrogen was fed untilthe pressure in the system was reached2.0 kg/cm² (gauge pressure). As aresult, 43.2 g of an ethylene/1-hexene copolymer (WAX 3) having Mn of2,100, a 1-hexene content of 3.4 mol %, a density of 917 kg/m³, acrystallizing temperature of 93° C. and a B value of 1.025 as shown inTable 1 was obtained.

[Preparation Example 4]

[0084] <Preparation of Ethylene/α-Olefin Copolymer>

[0085] Polymerization was carried out in the same manner as inPreparation Example 1, except that 910 ml of hexane and 90 ml of4-methyl-1-pentene as an α-olefin component were placed and hydrogen wasfed until the pressure in the system was reached 2.0 kg/cm² (gaugepressure). As a result, 41.2 g of an ethylene/4-methyl-1-pentenecopolymer (WAX 4) having Mn of 2,000, a 4-methyl-1-pentene content of3.7 mol %, a density of 918 kg/m³, a crystallizing temperature of 93° C.and a B value of 1.027 as shown in Table 1 was obtained.

[Preparation Example 5]

[0086] <Preparation of Ethylene/α-Olefin Copolymer>

[0087] Polymerization was carried out in the same manner as inPreparation Example 1, except that 935 ml of hexane and 65 ml of1-butene as an α-olefin component were placed and hydrogen was fed untilthe pressure in the system was reached 3.5 kg/cm² (gauge pressure). As aresult, 31.2 g of an ethylene/1-butene copolymer (WAX 5) having Mn of600, a 1-butene content of 5.2 mol %, a density of 920 kg/m³, acrystallizing temperature of 92° C. and a B value of 1.040 as shown inTable 1 was obtained.

[Preparation Example 6]

[0088] <Preparation of Ethylene/α-Olefin Copolymer>

[0089] Polymerization was carried out in the same manner as inPreparation Example 1, except that 935 ml of hexane and 65 ml of1-butene as an α-Olefin component were placed and hydrogen was fed untilthe pressure in the system was reached 1.0 kg/cm² (gauge pressure). As aresult, 38.8 g of an ethylene/1-butene copolymer (WAX 6) having Mn of4,000, a 1-butene content of 5.7 mol %, a density of 920 kg/m³, acrystallizing temperature of 92° C. and a B value of 1.037 as shown inTable 1 was obtained.

[Preparation Example 7]

[0090] <Preparation of Ethylene/α-Olefin Copolymer>

[0091] Polymerization was carried out in the same manner as inPreparation Example 1, except that 935 ml of hexane and 60 ml of1-butene as an α-Olefin component were placed and hydrogen was fed untilthe pressure in the system was reached 1.0 kg/cm² (gauge pressure). As aresult, an ethylene/1-butene copolymer (WAX 7) having Mn of 2,200, a1-butene content of 3.5 mol %, a density of 930 kg/m³, a crystallizingtemperature of 98° C. and a B value of 1.027 as shown in Table 1 wasobtained.

[Preparation Example 8]

[0092] <Preparation of Ethylene/α-Olefin Copolymer>

[0093] Polymerization was carried out in the same manner as inPreparation Example 1, except that 935 ml of hexane and 63 ml of1-butene as an α-Olefin component were placed and hydrogen was fed untilthe pressure in the system was reached 1.0 kg/cm² (gauge pressure). As aresult, an ethylene/1-butene copolymer (WAX 8) having Mn of 1,900, a1-butene content of 5.0 mol %, a density of 925 kg/m³, a crystallizingtemperature of 96° C. and a B value of 1.035 as shown in Table 1 wasobtained.

[Comparative Preparation Example 1]

[0094] <Preparation of Catalyst>

[0095] In a 1.5-liter glass autoclave, 25 g of commercially availableanhydrous magnesium chloride was suspended in 500 ml of hexane. Thesuspension was maintained at 30° C., and with stirring, 92 ml of ethanolwas dropwise added over a period of 1 hour, followed by reaction for 1hour. After the completion of the reaction, 93 ml of diethylaluminummonochloride was dropwise added over a period of 1 hour, followed byreaction for 1 hour. After the completion of the reaction, 90 ml oftitanium tetrachloride was dropwise added, and the temperature of theautoclave was raised to 80° C., followed by reaction for 1 hour.

[0096] After the completion of the reaction, the solids were washed withhexane by decantation until no titanium liberated was detected. Theobtained solids were suspended in hexane to give a hexane suspension,and the titanium concentration of the hexane suspension wasquantitatively determined by titration. This hexane suspension was usedfor the following experiment.

[0097] <Preparation of Ethylene/α-Olefin Copolymer>

[0098] In a 2-liter stainless steel autoclave thoroughly purged withnitrogen, 930 ml of hexane and 70 ml of 1-butene were placed, andhydrogen was fed until the pressure in the system was reached 20.0kg/cm² (gauge pressure). The temperature in the system was raised to170° C., and 0.1 mmol of triethylaluminum, 0.4 mmol ofethylaluminumsesquichloride and 0.008 mmol in terms of titanium atom ofthe titanium component obtained above were forced into the autoclavewith ethylene to initiate polymerization. Thereafter, only ethylene wascontinuously fed to maintain the total pressure at 40 kg/cm² (gaugepressure), and polymerization was conducted at 170° C. for 40 minutes.

[0099] After a small amount of ethanol was added to the system toterminate the polymerization, the unreacted ethylene and 1-butene in thesystem was purged off. The obtained polymer solution was dried overnightat 100° C. under reduced pressure. As a result, 129 g of anethylene/1-butene copolymer (WAX 9) having Mn of 2,000, a 1-butenecontent of 5.4 mol %, a density of 917 kg/m³, a crystallizingtemperature of 101° C. and a B value of 1.023 as shown in Table 1 wasobtained.

[Comparative Preparation Example 2]

[0100] <Preparation of Ethylene/α-Olefin Copolymer>

[0101] Polymerization was carried out in the same manner as inComparative Preparation Example 1, except that 850 ml of hexane and 150ml of 4-methyl-1-pentene as an α-Olefin component were placed andhydrogen was fed until the pressure in the system was reached 21.0kg/cm² (gauge pressure). As a result, 99 g of anethylene/4-methyl-1-pentene copolymer (WAX 10) having Mn of 2,100, a4-methyl-1-pentene content of 3.7 mol %, a density of 919 kg/m³, acrystallizing temperature of 105° C. and a B value of 1.015 as shown inTable 1 was obtained.

[Comparative Preparation Example 3]

[0102] <Preparation of Ethylene/α-Olefin Copolymer>

[0103] Polymerization was carried out in the same manner as inPreparation Example 1, except that no α-Olefin component was placed,1,000 ml of hexane was placed, and hydrogen was fed until the pressurein the system was reached 2.5 kg/cm² (gauge pressure). As a result, 34.4g of an ethylene polymer (WAX 11) having Mn of 2,000, a density of 977kg/m³ and a crystallizing temperature of 126° C. as shown in Table 1 wasobtained.

[Comparative Preparation Example 4]

[0104] <Preparation of Ethylene/α-Olefin Copolymer>

[0105] Polymerization was carried out in the same manner as inPreparation Example 1, except that 920 ml of hexane and 80 ml of propenewere placed. As a result, 29.9 g of an ethylene/1-butene copolymer (WAX12) having Mn of 1,800, a propene content of 11.2% by mol, a density of897 kg/m³, a crystallizing temperature of 81° C. and a B value of 1.040as shown in Table 1 was obtained. TABLE 1 (List of basic properties ofethylene/α-olefin copolymer (a) ) Name of Left-hand Crystallizationethylene/ α-Olefin Number-average Density member of temperature α-olefinType of content molecular (D) the formula (Tc) Preparation copolymerα-olefin (mol %) weight (Mn) (kg/m³) (1) (° C.) B value Example WAX1propene 7.3 2050 920 94.9 93 1.051 Prep. Ex. 1 WAX2 1-butene 5.6 1900920 94.9 93 1.038 Prep. Ex. 2 WAX3 1-hexene 3.4 2100 917 93.5 93 1.025Prep. Ex. 3 WAX4 4-methyl- 3.7 2000 918 93.9 93 1.027 Prep. Ex. 41-pente WAX5 1-butene 5.2 600 920 94.9 92 1.040 Prep. Ex. 5 WAX61-butene 5.7 4000 920 94.9 92 1.037 Prep. Ex. 6 WAX7 1-butene 3.5 2200930 99.9 98 1.027 Prep. Ex. 7 WAX8 1-butene 5.0 1900 925 97.4 96 1.035Prep. Ex. 8 WAX9 1-butene 5.4 2000 917 93.5 101 1.023 Comp. Prep. Ex. 1WAX10 4-methyl- 3.7 2100 919 94.4 105 1.015 Comp. 1-pente Prep. Ex. 2WAX11 none 0 2000 977 124.9 126 — Comp. Prep. Ex. 3 WAX12 propene 11.21800 897 83.4 81 1.040 Comp. Prep. Ex. 4

Examples 1-8, Comparative Examples 1-4

[0106] Using the ethylene/α-Olefin copolymers (ethylene polymer in caseof Comparative Example 3) obtained in Preparation Examples andComparative Preparation Examples mentioned above, cable jellies wereprepared in the following manner, and the properties of the cablejellies were evaluated. The results are shown in Table 2.

[0107] In Examples and Comparative Examples, oil drip properties andbodying temperatures of the cable jellies were evaluated by thefollowing methods.

[0108] <Preparation of Cable Jelly>

[0109] The total amount of 30 g of a sample consisting of the componentsshown in Table 2 was weighed and placed into a 100-ml glass beaker andsufficiently blended at about 130° C. by an oil bath. (For stirring,small-sized three turbine blades were used. number of revolutions: 100revolutions/min, stirring time: 30 minutes)

[0110] <Evaluation of Oil Drip Properties>

[0111] A glass funnel (diameter of conical part: 55 cm, length of leg: 1cm) stopped by inserting a glass bar into the leg was maintained at 130°C. for not shorter than 30 minutes in an oven. Then, the cable jellyprepared as above was poured into the conical part of the glass funnelwith maintaining the funnel at 130° C. The glass funnel was slowlycooled to room temperature over a period of about 12 hours, then theglass bar was slowly drawn out from the leg, and the glass funnel wasallowed to stand still for 24 hours in a circulating oven at 80° C.Then, the whole amount of the oil having fallen from the leg of thefunnel onto a beaker used as a receiver was measured.

[0112] <Measurement of Bodying Temperature>

[0113] Temperatures at which a melt viscosity, isothermally measured bya Brookfield viscometer, of the cable jelly prepared as above exhibits aconstant value (no increase by not less than 2%) for 30 minutes aremeasured, and the lowest temperature among them is taken as a bodyingtemperature. TABLE 2 (Evaluation of cable jelly properties) Compositionof cable jelly (weight %) Evaluation of properties Ethylene/α-olefin Oildrip properties Bodying temperature Polybutene (d) Oil (e) copolymer (a)(mg/amount-jelly) (° C.) Aimed value not more than 100 not higher than102 Ex. 1 55 37 WAX1 8 80 97 Ex. 2 55 37 WAX2 8 10 97 Ex. 3 55 37 WAX3 880 97 Ex. 4 55 37 WAX4 8 90 97 Ex. 5 55 37 WAX5 8 90 98 Ex. 6 55 37 WAX68 20 96 Ex. 7 55 37 WAX7 8 1 102 Ex. 8 55 37 WAX8 8 5 100 Comp. Ex. 1 5537 WAX9 8 1700 105 Comp. Ex. 2 55 37 WAX10 8 1900 109 Comp. Ex. 3 55 37WAX11 8 40 129 Comp. Ex. 4 55 37 WAX12 8 not less than 3000 82

What is claimed is:
 1. An additive (b) for a communication cable filler,containing as a main component an ethylene/α-Olefin copolymer (a) havinga number-average molecular weight (Mn), measured by gel permeationchromatography (GPC), of 500 to 5,000 and having a crystallizingtemperature (Tc (° C.), rate of temperature decrease: 2° C./min)measured by a differential scanning calorimeter (DSC) and a density (D(kg/m³) ) measured by a density gradient tube method, said Tc and Dsatisfy the following formula (1): 0.501×D(kg/m³)−366≧Tc(° C.)  (1). 2.The additive (b) for a communication cable filler as claimed in claim 1,wherein the ethylene/α-Olefin copolymer (a) has a crystallizingtemperature (Tc (° C.), rate of temperature decrease: 2° C./min)measured by a differential scanning calorimeter (DSC) and a density (D(kg/m³) measured by a density gradient tube method, said Tc and Dsatisfy the following formula (2): 0.501×D(kg/m³)−367≧Tc(° C.)  (2). 3.The additive (b) for a communication cable filler as claimed in claim 1or 2, wherein the ethylene/α-Olefin copolymer (a) is anethylene/α-Olefin random copolymer obtained from ethylene and anα-Olefin of 3 to 10 carbon atoms and having an ethylene componentcontent of 90 to 99 mol % and an α-Olefin component content of 10 to 1mol %.
 4. The additive (b) for a communication cable filler as claimedin any one of claims 1 to 3, wherein the ethylene/α-Olefin copolymer (a)is obtained by feeding ethylene, an α-Olefin and hydrogen to thepolymerization system in the presence of a metallocene catalystcontaining as a main component a compound, having a cyclopentadienylgroup, of a transition metal selected from the group consisting oftitanium, zirconium, hafnium and vanadium to copolymerize ethylene withthe α-Olefin.
 5. The additive (b) for a communication cable filler asclaimed in any one of claims 1 to 4, wherein a B value calculated basedon a chart of ¹³C-NMR (270 MHz) of the ethylene/α-Olefin copolymer (a)and expressed by the following formula (3), B=P _(OE)/(2×·P _(O) P_(E))  (3) wherein P_(E) is a molar fraction of the ethylene componentin the copolymer, P_(O) is a molar fraction of the α-Olefin component,and P_(OE) is a molar fraction of α-Olefin-ethylene sequences in the alldyad sequences, with the proviso that the molar fraction of eachcomponent is a value calculated except the terminal component, and the Bvalue satisfies the following formula (4), 1.0<B<2  (4).
 6. Acommunication cable filler (c) containing as an essential component theadditive (b) for a communication cable filler of claim 1 or 2 andcomprising: (X) 40 to 90% by mass of polybutene (d) having anumber-average molecular weight of 200 to 2,400, (Y) 1 to 50% by mass ofan oil (e), and (Z) 1 to 15% by mass of the ethylene/α-Olefin copolymer(a) of any one of claims 1 to
 5. 7. The communication cable filler (c)as claimed in claim 6, having properties that in the oil drip test (REAPE-39 method, 80° C.×24 hr), any jelly and any oil do not fall from thefunnel, and after standing for 24 hours, the total amount of the jellyand the oil adhering inside the leg of the funnel is not more than 20mg.